1. Field of the Invention
The present invention relates to a sensor for detecting a physical amount, such as pressure or acceleration, and more particularly to a pressure sensor having a sensor chip and a circuit for processing sensor signals mounted on a cylindrical stem that includes a diaphragm.
2. Description of Related Art
An example of this kind of pressure sensor is disclosed in JP-A-2001-272297. The pressure sensor is composed of a cylindrical stem having a diaphragm at one axial end. A pressure to be measured is introduced into the cylindrical stem from an opening formed at the other axial end of the stem, and the diaphragm distorts according to an amount of pressure applied thereto. A sensor chip for outputting an electrical signal representing the distortion of the diaphragm is connected to the outer surface of the diaphragm. A circuit board for processing the electrical signal is disposed around the sensor chip on a plane parallel to the outer surface of the diaphragm on which the sensor chip is mounted.
Because the sensor chip and the circuit board are positioned in parallel to each other in the conventional pressure sensor, a size of the pressure sensor in the radial direction of the stem becomes large. This positioning also makes the sensor structure complex.